import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree2 {
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }

    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode A = new TreeNode('A');
        TreeNode B = new TreeNode('B');
        TreeNode C = new TreeNode('C');
        TreeNode D = new TreeNode('D');
        TreeNode E = new TreeNode('E');
        TreeNode F = new TreeNode('F');
        TreeNode G = new TreeNode('G');
        TreeNode H = new TreeNode('H');
        A.left = B;
        A.right = C;
        B.left = D;
        B.right = E;
        C.left = F;
        C.right = G;
        D.left = H;
        return A;
    }

    // 前序遍历
    //根 左 右
    public void preOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        System.out.print(root.val + " ");
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    //左 根 右
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        inOrder(root.left);
        System.out.print(root.val + " ");
        inOrder(root.right);
    }

    // 后序遍历
    // 左 右 根
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val + " ");
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    int size(TreeNode root) {
        if (root == null) {
            return 0;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
        return nodeSize;
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        return size2(root.left) + size2(root.right) + 1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    int getLeafNodeCount1(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.left == null && root.right == null) {
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
        return leafSize;
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root == null) {
            return 0;
        }
        if (root.right == null && root.left == null) {
            return 1;
        }
        return getLeafNodeCount2(root.right) +
                getLeafNodeCount2(root.left);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if (root == null || k < 0) {
            return 0;
        }
        if (k == 1) {
            return 1;
        }
        int tmp = getKLevelNodeCount(root.left, k - 1) +
                getKLevelNodeCount(root.right, k - 1);
        return tmp;
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if (root == null) {
            return 0;
        }
        int tmp1 = getHeight(root.left);
        int tmp2 = getHeight(root.right);
        return tmp1 > tmp2 ? tmp1 + 1 : tmp2 + 1;
    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if (root == null) {
            return null;
        }
        if (root.val == val) {
            return root;
        }
        TreeNode tmp1 = find(root.left, val);
        if (tmp1 != null) {
            return tmp1;
        }
        TreeNode tmp2 = find(root.right, val);
        if (tmp2 != null) {
            return tmp2;
        }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if (root == null) {
            return;
        }
        Queue<TreeNode> ret = new LinkedList<>();
        ret.offer(root);
        while (!ret.isEmpty()) {
            TreeNode tmp = ret.poll();
            System.out.print(tmp.val + " ");
            if (tmp.left != null) {
                ret.offer(tmp.left);
            }
            if (tmp.right != null) {
                ret.offer(tmp.right);
            }
        }
    }

    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if (root == null) {
            return true;
        }
        Queue<TreeNode> qu = new LinkedList<>();
        qu.offer(root);
        while (!qu.isEmpty()) {
            TreeNode cur = qu.poll();
            if (cur != null) {
                qu.offer(cur.left);
                qu.offer(cur.right);
            } else {
                break;
            }
        }
        //判断队列剩下的值 是否有 非null的数据
        while (!qu.isEmpty()) {
            TreeNode pop = qu.poll();
            if (pop != null) {
                return false;
            }
        }
        return true;
    }
}
